1. Field of the Invention
The present invention relates to an inkjet recording apparatus for executing recording on a medium by ejecting ink droplets onto the medium and depositing the ink droplets thereon, and more particularly, to an inkjet recording apparatus for ejecting ink in a direction opposite to the direction of gravity.
2. Description of the Related Art
Recent developments in personal computers have caused remarkable technical innovations in recording technologies used in output apparatuses for personal computers. Among these recording technologies, inkjet recording is spotlighted as a technology used in an output apparatus for outputting not only characters but also images, and in particular, images such as photographs for which multigradation, multi-color, and high resolution are required.
Inkjet recording apparatuses print characters or create an image by outputting electric signals based on image information, ejecting a minute amount of ink droplets from nozzles, which are disposed in great numbers ordinarily, on demand through an electro-dynamic transducer, and depositing the ink droplets onto a medium such as a paper and the like.
Known well among these inkjet recording apparatuses is a recording apparatus which ejects ink in a direction along the gravity direction, that is in a downward direction and a recording apparatus which injects ink in a vertical direction normal to the gravity direction.
FIG. 1 is a sectional view showing a main portion of a conventional inkjet recording apparatus. In this recording apparatus, an inkjet recording head is arranged so as to eject ink in a direction along the gravity direction, that is, in a downward direction.
In the inkjet recording apparatus shown in FIG. 1, a recording head 101 and an ink tank 102 are mounted on a carriage 103, wherein the recording head 101 ejects ink onto an upper surface of a medium M and forms an image thereon, and the ink tank 102 accommodates ink to be supplied to the recording head 101. The carriage 103 is supported by two sliding shafts 105a and 105b and reciprocated by a carriage drive motor (not shown) through a timing belt (not shown) in a direction (vertical to the figure) which is normal to a direction in which the medium M is transported (right to left direction on the figure).
A head fixing cover 104 is mounted on the carriage 103 so that the recording head 101 can be fixed on the carriage 103 with a high degree of precision.
Note that these two sliding shafts 105a and 105b support the carriage 103 and determine a scanning direction thereof as well as regulate a distance between an ink ejecting port surface 101a of the recording head 101 and the medium M facing the ink ejecting port surface 101a to permit an image of high accuracy to be formed on the medium M.
As the carriage 103 moves, the inkjet recording apparatus creates an image for each one scan on the upper surface of the medium M by ejecting ink from the recording head 101 during reciprocating movement of the recording head 101 while alternately repeating the movement of the recording head 101 and transportation of the medium M at a each predetermined pitch.
A pair of sheet feed rollers 106a and 106b, which constitute a transportation unit for transporting the medium M, are disposed upstream of the carriage 103 with respect to a transporting direction of the medium M. The medium M is supplied between the sheet feed rollers 106a and 106b from an auto-sheet-feeder (not shown) or a cassette (not shown) mounted on the recording apparatus. Note that the sheet feed roller 106b is driven by a drive unit (not shown) through a drive gear 107.
A guide member (not shown) is disposed downstream of the sheet feed rollers 106a and 106b with respect to the transporting direction of the medium M. The guide member prevents the ink ejecting port surface 101a from coming into contact with the medium M by preventing floating and twisting of the medium M at a position where it faces the ink ejecting port surface 101a. In addition to the above, the guide member keeps a distance between the ink ejecting port surface 101a and the upper surface of the medium M constant, thereby maintaining a position where ink reaches the medium M at a high degree of precision.
Further, a pair of sheet discharge rollers 108a and 108b are disposed downstream of the carriage 103 with respect to the transporting direction of the medium M. When the medium M arrives between the sheet discharge rollers 108a and 108b, it is further transported mainly by the sheet discharge rollers 108a and 108b thereafter, and the medium M, on which an image is created by the recording head 101, is discharged to the outside of the recording apparatus.
It is known in recording by inkjet that execution of preliminary ejection is an effective means for achieving stable recording. A preliminary ejection receiver (which also is referred to as an ejection without ink receiver) has the function of receiving ink that is ejected from a recording head at a predetermined position outside the region where recording can be executed to a medium, prior to a recording operation and for supplying the thus received ink to a waste ink processing system.
While there are several reasons why this arrangement is necessary, one particular reason is to discharge ink which is condensed in nozzles when a recording apparatus is not used for a long period.
When a recording operation is resumed after the recording apparatus is brought to rest for a long time, ink condensed at positions near to ejecting ports of nozzles is ejected first, and then ink in the interiors of the nozzles and ink from an ink supply system located rearward of the nozzles are gradually ejected. An image recorded at that time is such that a beginning portion of the image has a deep tone, and an intrinsic tone of the ink is gradually reproduced toward a rear portion thereof, which results in an uneven tone. In particular, when uniform half-tones of 50%, 25% and the like which are adjacent each other are recorded on a white medium, a portion having a deep tone is formed first on the medium to be recorded and the tone becomes lighter toward a rear portion thereof, which makes irregularity of tone particularly conspicuous on the medium to be recorded.
To prevent occurrence of the above problem, an image is usually formed on a medium M after ink condensed in nozzles is discharged using a preliminary ejection receiver (ejection without ink receiver) as described above.
In FIG. 1, a preliminary ejection receiver 109 for receiving ink preliminarily ejected from the recording head 101 is disposed with its opening facing a direction opposite to the gravity direction, that is, in an upward direction. In the recording apparatus, the preliminary ejection receiver 109 is disposed outside a region, where recording can be executed by the recording head 101 to the medium M. More specifically, the preliminary ejection receiver 109 is disposed at a position in the vicinity of a terminal end in a moving region of the carriage 103 which moves along the sliding shafts 105a and 105b. As a result, when the carriage 103 moves to the terminal end, the ink ejecting port surface 101a of the recording head 101 mounted on the carriage 103 faces the opening of the preliminary ejection receiver 109. Note that an absorption body 110 is disposed in the preliminary ejection receiver 109 to hold the preliminarily ejected ink.
A waste ink absorption body 111 and a waste ink holding member 112 are disposed in the inkjet recording apparatus below the above respective arrangements to cope with a case in which ink accidentally drops from the recording head 101.
As described above, in a downward printing type recording apparatus, a preliminary ejection receiver is disposed below a recording head with its opening facing upward, and ink ejected into the preliminary ejection receiver drops downward due to gravity and is stored on a bottom portion. As a result, in the downward ejection type recording apparatus, no problem occurs as to accommodation of ink, which is ejected from a recording head into the preliminary ejection receiver, and no special device is necessary except provision of a drain for collecting waste ink.
As is apparent from the above explanation, it is preferable in an inkjet recording apparatus to eject ink in a downward direction along the gravity direction. This is because when problems arise in the recording apparatus, deposition of ink on an ink ejecting port forming surface of a recording head and on an electric circuit, contacts, and the like, which realize ejection of ink from nozzles, is prevented and occurrence of a greater problem can be avoided, because this arrangement permits ink to drop downward from the nozzles.
Another advantage of the downward ejection type inkjet recording apparatus is in that preliminarily ejected ink can be easily collected because ink received by the preliminary ejection receiver 109 is dropped downward by gravity and collected in the bottom portion. Still another advantage of this type of the recording apparatus is that, even if ink is ejected to the medium M in a large amount, it is difficult for the ink to flow downward therefrom because a recording surface of the medium M faces upward.
However, in the recording head arranged to eject ink downward along the gravity direction, ink paths in the nozzles must be kept at a pressure lower than atmospheric pressure (i.e., negative pressure) so that ink does not drop unintentionally from nozzles of a recording head during a recording operation. Various systems are employed as a means for generating the negative pressure. One simple system is arranged such that a soft tube having no ventilating property is connected to a recording head at an end thereof and used as an ink supply path, an ink bag or the like is connected to the other end of the tube, and the ink bag is located at a position lower than ink ejecting ports in a recording apparatus. As a further example, there is a system having a head unit replaceably mounted on a carriage, wherein the head unit includes a recording head provided with ink ejecting ports and an ink storing unit which are arranged integrally each other, and the ink storing unit generates a negative pressure by impregnating a porous ink absorbing member with ink to be ejected. In this case, in the downward ejection type inkjet recording apparatus, since the ink tank 102 is disposed above the ink ejecting port surface 101a of the recording head 101, when a negative pressure in the ink tank 102 is reduced even slightly, the negative pressure in the ink tank 102 is liable to be made unstable when the recording head 101 moves, and ink is liable to flow downward from an extreme end of the recording head 101. Thus, to stabilize the negative pressure in the ink tank 102, a structure of an ink path in the ink tank 102, e.g., the position, size, and density of the absorption body, are variously devised, which increases complexity of a structure of the ink tank 102.
In the downward ejection type inkjet recording apparatus, a recording surface of a medium M faces upward. Thus, when recording is executed to a plurality of mediums M, they are outputted with pages ordered reversely unless they are discharged upside down by being U-turned after recording has been completed.
To solve problems of the generation of the negative pressure and reverse stacking of sheets as described above, there is proposed to employ an upward ejection type recording apparatus for ejecting ink in an upward direction which is opposite to the gravity direction.
When the upward ejection type recording apparatus is employed, no special device is necessary to generate a negative pressure because an ink ejecting port forming surface of a recording head is located above a liquid level of ink to be supplied.
Furthermore, the upward ejection type recording apparatus can realize face down recording in which a recording surface of a medium faces downward, which permits the medium to be outputted, even if recording is executed to a plurality of mediums, with a proper order of pages even if it is not discharged upside down.
In addition to the above-mentioned, it is also possible to provide an arrangement capable of, for example, simultaneously executing printing on both surfaces of a medium to be recorded using recording heads for ejecting ink downward and upward at the same time.
It is necessary to execute preliminary ejection even in the recording apparatus for ejecting ink in the upward direction against the gravity direction in order to stabilize recording.
In this case, a preliminary ejection receiver is disposed above a recording head with an opening facing downward. When the preliminary ejection receiver of the downward ejection type recording apparatus is used as it is in the upward ejection type recording apparatus, ink ejected toward a ceiling surface of the preliminary ejection receiver drops therefrom due to gravity or flows downward along a wall surface and returns toward the opening again. In a worst case, the ink returned to the opening drops to the outside of the preliminary ejection receiver from the opening and pollutes an ink ejecting port forming surface of the recording head and an interior of the recording apparatus. There is also a possibility of such problems as short circuit of electric contacts of the recording head, and the like.
In an arrangement of the conventional preliminary ejection receiver, a mechanism for collecting waste ink resulting from preliminary ejection and a place where the waste ink is stored are necessary, which makes the recording apparatus itself complex and increases its size.
Accordingly, it is an object of the present invention, which was made in view of the above problems, to provide an inkjet recording apparatus capable of preventing ink ejected into a preliminary ejection receiver from leaking from an opening as well as capable of simplifying an arrangement of the recording apparatus and reducing a size of the apparatus.
To achieve the above object, in an inkjet recording apparatus of the present invention including a preliminarily ejected ink receiver for receiving ink ejected in preliminary ink ejection which is executed to maintain and recover an ink ejection performance of a recording head for recording an image on a medium by ejecting ink from ejecting ports in an upward direction which is a direction against the gravity direction and which does not contribute to recording, the inkjet recording apparatus is characterized in that the preliminarily ejected ink receiver includes an opening and an ink leakage prevention mechanism, the opening acting an inlet of the preliminarily ejected ink, and the ink leakage prevention mechanism preventing the ink preliminarily ejected into the preliminarily ejected ink receiver from leaking from the opening to the outside of the preliminarily ejected ink receiver along the gravity direction.
Further, in an inkjet recording apparatus of the present invention including a preliminarily ejected ink receiver for receiving ink ejected in preliminary ink ejection which is executed to maintain and recover an ink ejection performance of a recording head for recording an image on a medium by ejecting ink from ejecting ports in an upward direction which is a direction against the gravity direction and which does not contribute to recording, the inkjet recording apparatus is characterized in that the recording head is disposed obliquely with respect to the preliminarily ejected ink receiver associated therewith.
According to the inkjet recording apparatus of the preliminary ejection receiver, ink preliminarily ejected into the preliminary ejection receiver from the recording head through the opening is prevented from leaking to the outside of the preliminary ejection receiver from the opening thereof. Thus, it is possible to prevent an ink ejecting port forming surface of the recording head and the interior of the recording apparatus from being polluted with the ink.
It is preferable that the ink leakage prevention unit be composed of a ceiling member which inclines with respect to a horizontal direction. Ink which is preliminarily ejected into the preliminary ejection receiver from the recording device through the opening deposits on the ceiling member. According to this arrangement, the ink which is preliminarily ejected into the preliminary ejection receiver and deposited on the ceiling member flows downward along the ceiling member due to gravity. Thus, it is possible to discharge the preliminarily ejected ink to the outside of the preliminary ejection receiver without directing the ink toward the opening.
Further, a plurality of grooves may be formed on a surface of the ceiling member along the inclining direction of the ceiling member. According to this arrangement, since the grooves generate a capillary force, they can cause the preliminarily ejected ink to flow along the ceiling member without dropping the ink downward after they capture the ink. As a result, leakage of ink from the opening can be more reliably prevented.
A projection projecting upward may be disposed around an edge of the opening of the preliminary ejection receiver. With this arrangement, even if the preliminarily ejected ink drops from the ceiling member around a periphery of the opening, the ink is dammed around the periphery of the opening by the projection. Thus, there is no possibility that the ink leaks to the outside of the preliminary ejection receiver by passing through the opening.
An ink absorption body may be disposed around the edge of the opening of the preliminary ejection receiver, which can more effectively prevent drop and leakage of ink from the opening.
The preliminary ejection receiver may include an ink discharge unit for discharging ink accommodated therein to the outside of the preliminary ejection receiver. The ink absorbing body may be continuously formed in the ink discharge unit and the preliminary ejection receiver.
The inkjet recording apparatus may include a carriage on which the recording head is mounted and which is scanned with respect to the medium. A preliminarily ejected ink receiver is disposed at a position which is located outside a region where an image can be recorded on the medium and which faces an ink ejecting port surface of the recording head having been moved outside the region by the carriage.
The preliminarily ejected ink receiver may include a heat generating unit for evaporating a liquid component of ink preliminarily ejected from the recording head and deposited on the heat generating unit.
According to the inkjet recording apparatus of the present invention arranged as described above, a liquid component of ink preliminarily ejected from the recording head and deposited on the heat generating unit is evaporated in a very short time, and a solid component of the ink is firmly fixed on a surface of the heat generating unit. Since the preliminarily ejected ink can be rapidly dried as described above, the ink can be prevented from dropping downward from the preliminary ejection receiver later. Since the ink does not drop downward from the preliminary ejection receiver, it is not necessary to provide a waste ink absorption body or the like in the recording apparatus, which can simplify an arrangement of the recording apparatus and reduce its size.
It is preferable to provide a cleaner for removing the solid component of the ink firmly fixed on the surface of the heat generating unit after the liquid component of the ink deposited on the heat generating unit has been evaporated.
The inkjet recording apparatus may include a carriage on which the recording head is mounted and which is scanned with respect to the medium to be recorded. A preliminarily ejected ink receiver may be disposed at a position which is located outside a region where an image can be recorded on the medium to be recorded and which faces the ink ejecting port surface of the recording head having been moved outside the region by the carriage.
The inkjet recording apparatus of the present invention may include a carriage on which a recording head is mounted and a heat generating member. The recording head records an image on a lower surface of a medium by ejecting ink from ejecting ports upward against gravity. The carriage is scanned with respect to the medium to be recorded, and the heat generating member extends over a scanning range of the carriage along a scanning direction thereof, is disposed at a position facing the ink ejecting port surface of the recording head and evaporates a liquid component of ink preliminarily ejected from the recording head and deposited on the heat generating member.
According to the inkjet recording apparatus of the present invention, a region of the heat generating member for receiving the preliminarily ejected ink extends over a moving region of the carriage, and ink can be preliminarily ejected to the heat generating member while scanning the recording head mounted on the carriage. As a result, even if ink is continuously ejected, a liquid component of the ink can be sequentially and instantly evaporated on a surface of the heat generating member, which causes no insufficient evaporation of the ink. Further, since the heat generating member receives the preliminarily ejected ink in a wide region, a solid component of the ink dispersingly deposits on the surface of the heat generating member in a lengthwise direction, which can reduce the number of times the heat generating member must be cleaned.
Generation of heat from the heat generating member not only in a preliminarily ejecting operation but also in an image recording operation permits a medium to be heated from a back surface of a recording surface thereof in the image recording operation. With this operation, water of ink deposited on the recording surface can be rapidly dried, whereby a fixing time of ink to the medium can be reduced.
A cleaner for removing the solid component of the ink firmly fixed on the surface of the heat generating member after the liquid component of the ink deposited on the heat generating member has been evaporated may be mounted on the carriage in place of the recording head. With this arrangement, the solid component of the ink firmly fixed on the heat generating member can be removed by the cleaner by reciprocating the carriage in a scanning direction.
Further objects, features and advantages of the present invention will become apparent from the following description of the preferred embodiments with reference to the attached drawings.